See Table: Light Sources and Illumination for the radius that a light source illuminates and how long it lasts. The increased entry indicates an area outside the lit radius in which the light level is increased by one step (from darkness to dim light, for example).

In an area of bright light, all characters can see clearly. Some creatures, such as those with light sensitivity and light blindness, take penalties while in areas of bright light. A creature can’t use Stealth in an area of bright light unless it is invisible or has cover. Areas of bright light include outside in direct sunshine and inside the area of a daylight spell.

Normal light functions just like bright light, but characters with light sensitivity and light blindness do not take penalties. Areas of normal light include underneath a forest canopy during the day, within 20 feet of a torch, and inside the area of a light spell.

In an area of dim light, a character can see somewhat. Creatures within this area have concealment (20% miss chance in combat) from those without darkvision or the ability to see in darkness. A creature within an area of dim light can make a Stealth check to conceal itself. Areas of dim light include outside at night with a moon in the sky, bright starlight, and the area between 20 and 40 feet from a torch.

In areas of darkness, creatures without darkvision are effectively blinded. In addition to the obvious effects, a blinded creature has a 50% miss chance in combat (all opponents have total concealment), loses any Dexterity bonus to AC, takes a –2 penalty to AC, and takes a –4 penalty on Perception checks that rely on sight and most Strength– and Dexterity-based skill checks. Areas of darkness include an unlit dungeon chamber, most caverns, and outside on a cloudy, moonless night.

Characters with low-light vision (elves, gnomes, and half-elves) can see objects twice as far away as the given radius. Double the effective radius of bright light, normal light, and dim light for such characters.

Illuminating Darkness

Given how powerful it is to take away someone’s sight in this game, few topics share the three ‘C’s that make light and darkness such an important topic: Common, Crucial, and Confusing. This sidebar is meant to explain light and darkness so by the end, you will be armed and ready to run light and darkness in your games, even the edgiest of edge cases.

Lets start by covering a number of important guidelines for dealing with light and darkness in your game.

1. Let There Be Light

In the absence of darkness magic, light magic is fairly straightforward. Without magic involved, there are four light levels: darkness, dim light, normal light, and bright light. Each light spell tells you what light level it creates, and in what radius. So that’s not bad at all!

2. What a Nice Ambience

Darkness magic by itself isn’t too bad either, but it’s harder to deal with than light magic. Darkness spells first negate nonmagical light sources like lanterns and sunrods, and then they tell you how many steps to reduce the “ambient” light, and some of them can create a new fifth light level called supernatural darkness below darkness, in which even darkvision is useless (but the devil/darkfolk ability see in darkness still reigns supreme). However, there’s one tricky nuance in darkness magic, and that’s the question “what is ambient anyway?” The FAQ from October 2010 tells us a little more: it defines ambient light as “the light level from natural sources, such as the sun, moon, and stars—not torches, campfires, light spells, and so on.” This is a good start, but it leads into a debate about “natural.” So here’s the strongest rule of thumb for what kind of light is ambient, “If a creature is moving it around with them, it’s almost never ambient, and if the light is quite different in pockets instead of spread throughout an area uniformly, it’s probably not ambient (with exceptions for holes in the ceiling streaming down sunlight in patches, for example).” For example, in a cavern lit by luminescent fungi, that light is ambient. If a svirfneblin plucked some of the fungi and put them in a lantern-frame and carried them around, the light is not ambient. If a svirfneblin took some seeds and grew a cavern of the fungi equivalent to the first, it’s ambient. Use your judgment, but with an eye towards most corner cases not being ambient.

3. And Ne’er the Two Shall Meet

OK, we can do light, and we can do darkness. But what if the two of them meet? There’s quite a few interactions, including a special exception for the spell daylight, so first let’s focus on the basic interactions. From the descriptors and the spells themselves, we glean the following facts: Spells with the light descriptor only raise the light level within an area of a darkness descriptor spell if they are higher level than the darkness descriptor spell. Apparently also, darkness spells can counter or dispel light spells of equal or lower level (and light spells can do the same to darkness spells). So what does that mean?

4. I Counter Your Counter!

There are many ways to misinterpret the “counter or dispel” text for light and darkness spells. Here’s how that particular rule actually works. To counter a spell of the opposing descriptor, you ready an action just like any other counterspell. Just as normal for counterspell, the target of the spell must be within range (which, without Reach Spell metamagic, is touch for most light and darkness spells). If the target is in range, you automatically counter the opposing spell and it has no effect, just like always for counterspell. To dispel, you simply cast your spell on the same target (just like with enlarge person and reduce person) and then they cancel each other out, leaving no spell. Again, the range is usually touch and the target is the object that radiates the darkness or light; you can’t just touch an arbitrary spot within the darkness or light.

5. Pierce the Darkness

Now that we have those out of the way, let’s assume the more typical case where someone cast a darkness spell on one object, somebody else cast a light spell on another object, and the areas overlap. We’re still not dealing with daylight yet. Based on the rules of light and darkness, here’s how to adjudicate this situation within the overlap:

First, the darkness spell turns off nonmagical light sources and lowers the ambient light level. If there are multiple darkness spells, figure out the highest spell level (not caster level!)

Next, the light spells attempt to shine through. For every light spell, check to see if it has a higher spell level (not caster level!) than the highest spell level of any of the darkness spells. If so, that light spell has its normal effect, as per the spell. Do not reduce its light level again for the darkness spell; that already happened. This is true in all overlapping areas, as per the May 2013 FAQ, whether the light spell’s source object is within the area of darkness or not.

6. Here I Stand, in the Light of Day

OK, so what about daylight? We’ve been putting that one off until now because it simply doesn’t work like other light and darkness spells. As it says “Daylight brought into an area of magical darkness (or vice versa) is temporarily negated, so that the otherwise prevailing light conditions exist in the overlapping areas of effect.” Daylight comes in, if necessary right after those last two bullet points in section 5.

If no other light spell is sufficient to overcome the darkness spells in the overlapping area, and if there is a daylight spell active in the overlapping area, the daylight spell’s special negation clause kicks in (regardless of the spell level of daylight and the darkness spell; it just works, always). This means that you negate all the magical light changes in the area and bring it back to prevailing conditions. As a side effect of negating the magical darkness, those nonmagical light sources activate again (while they are not ambient, they were still part of prevailing conditions). Other magical light sources still are not active in the area; they had their chance to attempt to negate the darkness spells and didn’t, so they were not part of the prevailing light conditions, instead subsumed by daylight’s more powerful special negation clause.

7. Will Anyone Think of the Elves?

So what about low-light vision anyway? Those guys can see twice as far via light sources. However, they don’t change the actual radius of the magic at all. We’ll examine what that means for each step separately, using elves as an example instead of always saying “creatures with low-light vision” all the time:

In areas with light magic only, elves see twice as far. So with daylight, elves get 120 feet of bright light followed by 120 feet of one step up from normal.

In areas with darkness magic only, elves are affected by darkness spells in the same region. Since darkness spells quench the effects of nonmagical light sources before applying their reduction, elves should almost always be experiencing the same light level as everyone else (if supposedly “ambient” light was dispersed enough in pockets that the elf’s low-light vision was giving it a different light level, chances are the light wasn’t ambient to begin with). In the rare cases with odd pockets of ambient light, it is possible that an elf experiences a different light level in the darkness spell due to the ambient light being different for the elf.

In areas with both light and darkness magic, the elf being an elf does not change where the magics overlap. But where is that? The spells target an object, rather than stating an emanation. For the purpose of determining where light and darkness magics have an overlapping region, look at the spell and determine the farthest radius where it has an effect (for example, that would be 120 feet for daylight, 20 feet for darkness, and 40 feet for continual flame).